Thermostatic circuit-breaking apparatus for electrical heaters.



Jv. E. HARVEY.

THERMOSTATIC CIRCUIT BREAKING APPARATUS FOR ELECTRICAL HEATERS.APPLICATION FILED APR. 3. I9I5.

l. E. HARVEY.

THEIIMosIAIIc CIRCUIT BREAKING APPARATUS-F03 IQLECIIIICHAI IIE'AIEIIS.

v -APPLICATION FILED APR. 3- I9I5AI I 1,174,006.` l Pafentd Feb.29,1916..

3 SHEETS-SHEET 2.

. J. E. HARVEY. THERMCSTATIC CIRCUIT BREAKING APPARATUS POP ELECTRICALHEATEIIS.

APPLICATION FILED APIT. 3. 1915. 1,174,006. Petented Feb. 29,1916. 3SHEETS-SHEET 3. /55

To all 'whom t may concern.'

v JOHN E. HARVEY, 0F MILTON, MASSACHUSETTS.

i THEMOBTATC CIRCUIT-BREAKING APPARATUS FOB ELECTRICAL HEATEBS.

Specication of Letters Yatent.

I Patented Feb.'29, 1916.

Application lecl A111113, 1915. Serial No. 18,906.

Be it known that I, JOHN E. HARVEY, a citizen of the United States, -andresident of Milton, in the county of Norfolk and- State ofMassachusetts, have invented cer-v tain new and useful Improvements inThermostatic Circuit-Breaking Apparatus for Electrical Heaters, of whichthe following is a specification.

This invention relates to means for automatically breaking an electriccircuit -through a heating unit when the heat rises above apredetermined degree, and as here shown is embodied in a sterilizingapparatus, which includes a tank; a heating unit adapted to heat thebottom of the tank; a

, movable circuit-closing and breaking member in circuit with theheating unit, and held in circuit-breaking position; arresting meansadapted to hold said member in circuit-closing position;thermostaticmeans connected with said arresting means in such mannerthat upon the overheating of the bottom of the tank, in consequence ofthe evaporation of water therefrom, the said movable member is releasedand caused to break the circuit and thus discontinue the heat.

Of the accompanying drawings forming a part of this specification:Figure 1 represents a longitudinal section of a sterilizing apparatusembodying my invention, the plane of said section being indicated by theline 1--1 of Fig. 2; Fig. 2 represents a top plan view, the tank beingremoved, a part of the heating unit broken away and certain parts shownin section; Fig. 3 vrepresents a section on line 3-3 of Fig.2; Fig. 4represents a section on line 4 4 of 3, looking upwardly; Fig. 5represents a fragmentary elevation of a portion of the tank and thebracket and detent holder; Fig. 6

A represents a section on line 6 6 of Fig. 3; .Fig 7 represents aperspective view'of the bracket; Fig. 8 represents a perspective view pof the inne'r section of the detent lever; Fig.

9 is a view similar to Fig. 2, showing a different embodiment of theinvention; Fig. 10 represents a section on line 10-10 of Fig. 9; Fig. 11represents aV section on line 11-11 of Fig. 9; Fig. 12 represents afragmentary perspective view showing details hereinafter referred to.

Referring rst to Figs. 1 to 8 inclusive,- 12 represents a casing whichmay be of sheet metal and of rectangular form, and is supwith nuts 12b.

ported by a horizontal base 13 having a flange 13L which surrounds thelower edge portion ofthe casing, the base being provided with legs 13?.As here shown, the

\ horizontal portion of the base has an opening 13 covered by arelatively thin sheet metal bottom plate 13d, the other portions of thebase being preferably formed as a single casting. The casing is providedwith downwardly projecting bolts 12 offset inwardly om its inner surfaceand passing through holes in the base, said bolts being provided Thesaid bolts and nuts detachably secure the casing to the base and permitthe heating unit and other parts hereinafter described, supported by thebase, to be assembled before the casing, the tank, and the hereinafterdescribed thermostat and detent lever supported thereby are located onthe base.

14 represents a tank attached at its upper edge to-the upper edge of thecasing 12, the sides of the tank being preferably inclined, as shown byFigs. 1 and 3, to form an air space. -The bottom of the tank is elevatedabove the base to form a space in which the lhereinafter describedheating unit, the ther- I preferably interposed between the body 17 andthe bottom of the pan to prevent the downward radiation of heat. The panis supported and spaced from the base by bolts 2O attached to the bottomof the pan and passing through orifices in the base, the bolts eingseparable from the base and provided with nuts 21 bearing on oppo-sitesurfaces of the base, and detachably securing the bolts thereto.

The thermostat is composed of a brass tube 22 soldered or brazed alongits entire length to the bottom of the tank, and a steel rod 23, whichextends loosely through the tube 22. One end of the rod 23 is providedwith an adjustable head or abutment bearing on one end of the tube 22,'and preferably composed of two nuts 24 engaged with a threaded portionof the rod, one nut I section 30 is formed to detachably engage lockingthe other at the desired adjustment. One end of the tube 22 is solderedor brazed in a recess 27, formed for its reception in a fixed bracket 27(Fig. 7) which supports the inner section or member 28 of a swingingdetent, forming a part of the circuitbreaking and closing meanshereinafter described, controlled by the thermostat. The bracket 27includes rivet-engaging ears 27h bearing on the bottom of the tank; aperfol-ated ear 27 and an arm 27d havin a perforated ear 27e inalinement with the ear 27, the recess 27a being in an enlargement of thearm, and the bracket being referably cast'in one piece. The detenteversection 28 includes a bar 28a formed to enter the space between thebracket ears 27, 27, longitudinally perforated at 28b to receive afulcrum pin 29, which connects it with said ears; an arm 28 on one endof said bar slotted to receive an eye on one-end of the thermostat rod23, and perforated to receive a pintle 29, which connects the arm withsaid rod, and an elongated arm 28d, which extends at right angles withthe arm 28.

30 represents the outer member or section of the detent lever, thissection being adapted to engage a finger on the movable switch memberhereinafter described. The section 30 is pivoted at 31 to the arm 28dofthe inner section, and has two arms preferably of unequal length. Theshorter arm is pressed by a spring 32 against an adjustable stop screw33 on the arm 28d, said spring being coiled about a fixed stud 32 on thebase and having two arms, one bearing on a fixed stud 34 on the base,and the other on a stud 35 in the shorter arm of the lever section 30.The two lever sections 28 and 30 constitute a bell-crank lever, one armof which is formed by the arm28, and the other by the arm 28d, and theouter section 30. The object of the sectional construction of the leveris to permit the lateral adjustment of its outer end by the screw 33,for a purpose hereinafter described.

The outer end portion of the detent-lever a linger or projection on themovable member of a circuit-closing and breaking switch composed of afixed member and a movable member, said members, when in contact witheach other, closing the circuit through the heating unit, and breakingsaid circuit when separated. In this embodiment of the invention, I haveshown a circuit-closing and breaking device of the knife switch type,one member of the switch including two spaced-apart contact springs orstrips, 36, 36, while the other member includes a contact bridge 37formed to enter and bridge the space between said springs, as shown byFig. 1, thus closing an electric circuit, which includes the springs,the bridge and the 'is provided with a linger 38 formed to engage anotch 38 in the detent-lever section 30, as shown by Fig. 2. 80

40 represents a spring which is coiledon the fulcrum stud 39 and has twoarms, one bearing on a fixed stop stud 41, and the other on a stud 38don the carrier member 38. Said spring normally holds the carrier in theposition shown by Fig. 4 with contact bridge separated from the contactsprings, and 'the circuit broken. The engagement of the finger 38 withthe detentlever section 30 holds-the contacty bridge 37 in contact withthe contact springs, and prevents the spring 40 from acting.

44 represents a push piece movable in a guide 45 in the base, andconnected by a link 4 6 with the carrier member 38, said push piecebeing manually movable to move the finger 38 into engagement with thedetentlever notch 30, as shown by Fig. 2.

The electric circuit includes a wire 47 electrically connected by aconducting strip 47a (Fig. 2) with the contact spring 36, and with oneend of the resistance wire of the heating unit 16, a wire 48 connectingthe opposite end of the resistance wire with a plug 49, and a wire 50connecting the companion 105 plug 5l with a conducting strip 50aelectrically connected with the other contact spring 36a.

When the plugs 49, 51, are connected with a source of electrical energy,and the 11o contact bridge 37 is in the position shown by Figs. l and 2,the heating unit acts to heat the contents of the tank 14.

When the heat of the bottom of the tank exceeds a predetermined degree,as a result, for example, of the evaporation of water from the tank, theresulting expansion of the tube 22 of the thermostat exceeds that of therod 23, and the tube is caused by its elongation to act on the rodshoulder p formed by the nuts 24 and exert a pull on the rod. This pullswings the detent lever` in the direction of arrow m (Figs. 2, 4 and A8), and disengages its outer section 30 from the contact-bridge carrier,whereupon the v closing position by an inward movement of the pushpiece, the latter having been forced outwardly, when the circuit wasbroken.

The detent-lever section 30 has an oblique face 30b on which the finger38c bears, when moving to engage the notch 30a. The entire detent leverand the thermostat rod 23 are adapted to be displaced by the passage ofthe finger over the oblique face, the nuts 24 separating slightly fromthe end of the tube 22, after which the spring 32 presses the notchedend of the detent lever 'into engagement with the fin er.

The length of t e expanding movement of the tube 22 depends mainly onthe adjustment of the top screw 33 on the detent-leverA in effecting thedescribed adjustment.

In a sterilizing apparatus comprising a water tank, the adjustment ofthe screw 33 should be such that the circuit will be broken, when theheat of the tank bottom exceeds 212 F., the boiling point of water.Injurious overheating of the tank and its contents after the water boilsaway may be, therefore, automatically prevented.

While I have specified a knife switch as the preferred form ofcircuit-closing and breaking device, I do not limit myself thereto andmay use any suitable device including contact members, which areseparable by a spring acting on one of said members. The spring 40should be sufficiently strong to give the movable contact member acircuit-breaking movement, which is quick enough to obviate or minimizeinjury to the Contact members by sparking when they are being separated.e

In the above described embodiment of the invention the detent lever 30,which acts to release the movable switch member carrier 38, is moved bydirect mechanical connections between it and the thermostat member 22,when the latter is expanded by the heat of the tank.

To guard against failure to'break the circuit when the temperature risesto the predetermined point, it is necessary to soladjust the notch 30athat a relatively slight movement of the arm 30 will release the finger38. This renders the engagement of the notch and finger somewhatsensitive, so that they are liable to be prematurely or accidentallydisengaged by shocks or jars, such as those caused by moving theapparatus from one location to another. 'Io obviate this .objection Ihave devised the means shown by Figs. 9, 10, 11 and 12, whereby thethermostat formed by the members 22 and 23, instead of acting entirelythrough mechanical connections to break the circuit, acts to close acircuit through a secondary heating unit resistance, which in turn actson a secondary thermostat, the latter `in turn acting to release themovable member of the spring-impelled circuit-closing and breakingdevlce. In this embodiment of the invention the thermostat composed ofthe members 22 and 23 may be called the primary thermostat. The member23 is pivoted at 55 to the shorter arm of a lever 56 which is fulcrumedat 57 to ears 58 on a bracket 59 (Fig. 12) having ears '60 whicharkscrewed or riveted to the bottom of the ta The lever 56 has at theend of its longer arm a collar 56 of insulating material bearing on theupright arm of a bell-crank lever 61, which is fulcrumed at 61a to afixed bracket 62a attached to and insulated from the base.` Thehorizontal arm of the lever 61 projects under a lever 62 and is normallyout of-contact therewith, as shown by Fig. 11. The lever 62 is fulcrumedat 63 to av Xed bracket 64 insulated from the base, and is presseddownward by a spring 65 against an adjustable bearing screw 66 engaged'with the base, the lever being provided -with an insulated stud 67bearing on said screw.

The levers 61 and 62 and brackets 62, 64, constitute parts of anelectric circuit which includes a secondary heating unit 68, saidcurrent being'normally broken by the separation of the levers 61 and 62shown by Fig. 11. The lever 56 constitutes a means for closing saidcircuit by moving the lever 61 into contact with\the lever v62 when theprimary thermostat is expanded by heat.

The secondary heating unit is embedded in an elongated tube 70 ofinsulating material which contains the secondary thermo# stathereinafter described, said tube being supported by brackets 71, 72,attached to the base. One end of said unit is connected by a wire 73with the bracket 64 and the other end by a wire 7 4 with a contactspring,

or strip 75 which is the upper member of a pair of; spaced-apart contactsprings, the lower member of which is designated by the numeral 76, saidsprings being insulated from each other. The sprin 76 is connected bywire 77 with the termina plug 49, which is connected by wire 7 8 withone end of the tank heating unit 16', which is supported and arrangedlike the unit 16 previously described. A The opposite end of the unit 16is connected at 79 with a contact spring or strip 80- which isthe uppermember of a pair of spaced-apart contact springs, the lower member ofwhich is designated by the reference numeral 81, said springs beinginsulated from each other. The spring 81 is connected by'wire 82 withthe terminal plug 5l, and this plug in turn is connected with thebracket 62a by wire 83.

The secondary thermostat is composed of a brass tube 22 inclosed in thetubular holder of the secondary heating unit and attached at one end tothe bracket 72, and a steel'rod 23 extending through the tube and havingnuts 24 bearing on the free end of the tube. p

85 represents an oscillatory carrier fulcrumed at 86 on the base, andengaged by a spring 40, which has the same function as the spring 40, inthat it causes the breaking of the circuit through'the primary or tankheating unit, and the added function of causing the breaking of thecircuit through the secondary heating unit. In performing thesefunctions the spring 40 swings the carrier in the direction indicated byarrows 2, a, from the position shown by Fig. 9, and thus removes twocontact bridges 88 and 89 carried by it at opposite sides of its fulcrumfrom positions between and in contact with the contact springs 75, 76,and 80, 81, said bridges being insulated from the carrier 85.

When the apparatus is set for operation, the spring 40 is prevented fromperforming fits functions by a detent lever 90 fulcrumed The shorter armof said lever is pivoted at 92 to the rod 23 of the secondarythermostat, and the longer arm has a notch 93 engaging the reduced endof thecarrier 85. It will now be seen that when the apparatus is in thecondition shown by Figs. 9, 10 and 11, the primary heating circuit isclosed through the terminal plug 49, wire 78, unit 16', spring 80,bridge 89, spring 81, wire 82, and terminal plug 51, and the circuitthrough the secondary unit 68 is broken, because the lever 61 isnormally held out of contact with the lever 62, as shown by Fig. 11, bya spring 94. (Fig. 9).

When the primary thermostat is eX- panded by the heat of the tankbottom, it swings the lever 56 in the direction indicated by arrow 1/(Fig. 9) against the pressure of a spring 95 which normally holds saidlever in the position shown by Fig. 9; This movement of the lever 56moves the bell-crank lever 61, and causes it to make contact with thelever 62. The secondary heating unit circuit is now closed through theterminal plug 51, wire 83, bracket 62, lever 61, lever 62, bracket 64,wire 73, unit 68, wire 74, spring 75, bridge 88, spring 76, wirev 77 andterminal plug 49. The primary heating unit circuit remains closed untilthe secondary thermostat is sulficiently expanded by the heat developedby The last described construction avoidsany'premature or accidentalcircuit breaking which may occur when the apparatus is organized asfirst described, because at 210o the switch member carrier 38 must beheld in the notch 30EL while the current is heating the element 16. Atthe same time the detent lever 30 must release the carrier 38 at a fewdegrees above 212. Now according to the second construction, thesecondary thermostat may be at a temperature of approximately 200 whenthe 'secondary heating element is not in operation. When the secondarycircuit is closed, however, the secondary thermostat will be raised tofrom 400o to 500 in a few seconds, so that the carrier is released by arelatively ample movement of the lever 90 due to a rise in temperatureof from 300 to 400, instead of by a relatively slight movement of thedetent lever 30 due to a rise lin temperature of a few degrees.

The bearing screw 66 constitutes the equivalent of the screw 33 as anadjusting means for varying the extent of movement of the primarythermostat required for the performance of its function.

Each ofthe above described embodiments of the invention includes amovable carrier having circuit-breaking and closing means and normallyheld by means such as the spring 40. or thev spring 40 incircuit-breaking position, arresting means such as the detent 30, or thedetent 90, normally adapted to hold said carrier in circuitclosingposition, and thermostatic means, which may include the .tank-heatedthermostat only, and direct mechanical connections between saidthermostat and the arresting means, o1' may include the tankheated`primary thermostat and the secondary thermostat, the latterconstituting a member of the connections between the primary thermostatand the arresting means, and retarding the circuit-breaking action ofthe primary thermostat.

Having described my invention, I claim:

1. In combination, an electrical heating unit; a body heated thereby; amovable carrier having circuit-breaking and closing means in circuitwith said unit, said carrier being normally held in` circuit-breakingposition; arresting means normally adapted to hold said carrier in meansoperated by an increase of temperature of said body for making saidarresting means inoperative.

2. In combination, an electrical .heating unit; a body heated thereby; amovable carrier having circuit-breaking and closing means incircuit withsaid unit, a spring normally holding said carrier in circuitbreakingposition; arresting means normally adapted to hold said carrier incircuitclosing position; and thermostatic means operated by an increaseof temperature of said body for making said arresting means inoperative.

3. In combination, an electrical heating unit; a body heated thereby; amovable carrier having circuit-breaking and closing means in circuitwith said unit, said carrier `being normally held in circuit-breakingposition; arresting means normally adapted to hold said carrier incircuit-closing position; thermostatic means operated by an increase oftemperature of said body for making said arresting means inoperative;and adjusting means for regulating the action of the thermostatic means.

4. In combination, a primary heating circuit including an electricalheating unit; a body heated thereby; a secondary heating circuitincluding a thermostat-heating unit; .a movable carrier havingcircuit-breaking and closing members in circuit with said units, saidcarrier being normally held in circuit-breaking position; arrestingmeans normally adapted to hold said carrier in circuit-closing position;a primary thermostat arranged to be heated by said body; secondarycircuit-closing means actuated by said primary thermostat; a secondarythermostat arranged to be heated by the secondary heating unit; andmeans operated by the secondary thermostat for making said arrestingmeans inoperative.

5. In combination, an electrical heating unit; a body heated thereby; amovable carrier having circuit-closing and breaking means in circuitwith said unit, said carrier being normally held in circuit-breakingposition; arresting means normally adapted to hold said carrier incircuit-closing position; a thermostat arranged to be heated by saidbody; and means intermediate the thermostat and the arresting means forrendering the latter inoperative when the thermostat is expanded.

6.- In combination, an electrical heating unit; a body heated thereby; amovable carrier having circuit-closing and breaking means in circuitwith said unit, said carrier being normally held in circuit-breakingposition; arresting means normally adapted to hold said carrier incircuit-closing position; a thermostat composed of an elongated metaltube and a metal rod passing loosely through the tube and having ashoulder at one end bearing on one end of the tube; and meansintermediate the opposite end of the rod and the arresting means,

vfor rendering the latter,inoperative When the thermostat is expanded.

7 In combination, an electrical heating unit; a body heated thereby; amovable carrier having circuit-closing and breaking means in circuitwith. said unit', said carrier being normally held in circuit-breakingposition; a detent normally adapted to hold said carrier incircuit-closing position; a thermostat arranged to be heated by saidbody; and means intermediate the thermostat and detent for moving thelatter to a carrier-releasing position when the thermostat is expanded.

8. In combination, an electrical heating :soA

unit; a body heated thereby; a movable carrier having circuit-closingand breaking means in circuit-with said unit, said carrier beingnormally held in circuit-breaking position; a detent normally adapted tohold said carrier in circuit-closing position; la thermostat arranged tobe heated by said body; and means intermediate the thermostat and detentfor moving the latter to a carrier-releasing position When thethermostat is expanded, said means having provi-,

l stat and detent for moving the latter to a carrier-releasing positionWhen the thermostat is expanded, said -means including a secondaryheating unit, a secondary thermostat arranged to be heated'thereby, anddevices for closing the circuit through the secondary heating unit Whenthe thermostat heated bv the body is expanded.

10. In combination, a sterilizing tank; av

casing surrounding the tank; a base supportingthe casing and tank, saidbase and casing forming a space below the bottom of the tank; andheat-controlling means located in said space and comprising anelectrical heating unit arranged to heat the tank, a movable carrierhaving circuit-breaking and closing means in circuit with said unit,said carrier being normally held in circuitbreaking position, arrestingmeans normally adapted to hold said carrier in circuit-closing position,and thermostatic means operated by an increase of temperature of saidtank for making said arresting means inoperative.

11. In combination, an electrical heating unit; a body heated thereby; amovable carrier having circuit-closing and breaking means in circuitwith said unit, said carrier being normally held in circuit-breakingposition; a detent normally adapted to hold Said carrier incircuit-closing position; a.

thermostat arranged to be heated by said.

body;l and means intermediate the thermostat and detent for moving thelatter to a carrier-releasing position when the thermostat is expandesaid means including a secondary heating unit` a secondary thermostatarranged to be heated thereby, and devices for closing the circuitthrough the secondary heating unit when the thermostat heated by thebody is expanded, said means including a primary thermostat heated bythe tank, a secondary heating unit energized by the action of theprimary thermostat, and a secondary thermostat heated by the secondaryheating unit.

12. In combination, a sterilizingtank; a

casing surrounding the tank; a base supporting the casing and tank, saidbase and vcasing forming a space below the bottom of the tank; aheat-controlling meansvlocated in said space and comprising anelectrical heating unit arranged to heat the tank, a movable carrierhaving circuit-breaking and closing means in circuit with said unit,said carrier being normally held in circuit-breaking position, a detentnormally adapted to arrest said carrier in circuit-closing position, athermostat arranged to be heated by the tank, means intermediate thethermostat and detent for moving the latter to a carrier-releasingposition When the thermostat is expanded, and a push piece manuallymovable in the base and adapted to cause the re-engagement of thecarrier and detent.

In testimony whereof I have aliXed my signature.

JOHN E. HARVEY.

